The present invention relates to a new and improved construction of speech recognition device intended to control machines by means of words composed of phonetic elements.
It is known that certain prior art speech recognition devices operate with natural speech or with speech codes. These codes can consist of, for instance, combinations of vowels. However, the heretofore known speeches or codes have the following drawbacks:
1. They cannot be equally pronounced by individuals of different mother tongue. An Englishman, a Frenchman, a German, a Russian, an Arab and a Japanese cannot pronounce the known languages or codes with the same ease and precision;
2. The prior art speech recognition devices are complicated in construction and cannot detect such speech or codes without previous individual learning;
3. The known languages or codes are not capable of detecting whispered speech. The recognition of whispered speech is particularly then important for individuals which because of possible illness are inflicted with a temporary or continual loss of speech. Furthermore, whispered speech is necessary in order to maintain secrets during voice transmission. In principle there are no strict limits between whispered and normal (unvoiced and voiced) speech, so that with the heretofore known devices additional errors occur;
4. The known codes are not capable of being enlarged, something which is then particularly discernible when it is intended to use vowels;
5. The words and sentences of the known codes cannot be spoken with maximum speed and minimum effort, since the phonetic and linguistic rules are not designed for this purpose.